Most providers of digital maps rely on a very detailed topographical map database which stores the underlying data. For example, Ordnance Survey uses the very large scale topographic product OS MasterMap®, which records every feature larger than a few metres in one continuous dataset, and is constantly being updated.
A topographic feature is an abstraction of a real-world object. It is not the real-world object itself. For instance, the OS MasterMap® product is composed of discrete vector features, each of which has a feature type, geometry, and various feature attributes. More details about this product can be found in the manual OS MasterMap® Topography layer—User guide and technical specification, v1.12—March 2014.
The Topography Layer of the map database contains not only physically-apparent real-world objects, but also topographic concepts, such as inferred area feature boundaries. Currently, features within most topographic vector data (such as the data within the Topography Layer) exist in isolation with the only connection between features being the adjacency implied by coincident points (and lines) or the containment of some of the feature's points within an area or line feature. Each vector feature, whether area, line or point, has a location (which defines its shape in the case of areas and lines) and many other attributes.
There are many uses to which such data are put to derive more information about the region being described. For instance, to calculate the areas, lengths and distances between vector features. It is possible to automate such operations and such work has achieved estimates of, for example, the distance a delivery driver needs to walk to a front door or the extent of the land on which a built property exists.
However, whilst these applications are highly valuable, they do not provide opportunities for discovering new ways of categorising a feature or region because the rules-based approach is limited by the assumptions that the operator needs to make to devise the measurements to be made. Moreover, they do not provide opportunities for discovering errors in the underlying topographic data.